1. Field of the invention
The invention relates to an active stylus; in particular, to an active stylus signal identification method applied to a capacitive touch panel.
2. Description of the prior art
In general, the active stylus can be used with touch panels for smart phones, tablet computers and notebook computers. The active stylus signal transmitted by the active stylus is sent to the touch integrated circuit through the touch panel and processed by the touch integrated circuit to obtain the precise coordinates of the active stylus on the touch panel and the button state and pressure value of the active stylus. Then, this information will be transmitted to the system to complete the function of operating system or drawing line by the active stylus.
However, since different active stylus may regulate their respective protocols, in order to achieve a higher report rate, for example, 100 Hz or more, it is necessary to transmit coordinates and button state and pressure value and so on within a limited time (e.g., 15 ms). In other words, when the active stylus approaches the touch panel, the calculation amount of the touch IC is relatively large, and the methods of sensing the active stylus and the hand are different. Therefore, a common practice is that, when the active stylus approaches the touch panel, the touch sensing circuit will stop the touch sensing of the finger. Even the finger presses the touch panel, the touch panel does not react until the active stylus moves away from the touch panel. In other words, for the conventional touch panel, it is still difficult to achieve the effect of allowing the active stylus and the finger to operate the touch panel at the same time, resulting in many applications that require the active stylus and the finger to operate simultaneously.